get the max "absolute" integer in a vector

[JDT]

Hi,

Can someone provide me an example that uses std::max_elemen t()
(probablly the predicate version) to return the max "absolute" integer
in a vector? Your help is much appreciated.

Tony

ps.

// return the max integer in a vector
std::vector<int m;
....
std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end());

[Piyo]

Re: get the max &quot;absolute& quot; integer in a vector

JDT wrote:

Hi,
>
Can someone provide me an example that uses std::max_elemen t()
(probablly the predicate version) to return the max "absolute" integer
in a vector? Your help is much appreciated.
>
Tony
>
ps.
>
// return the max integer in a vector
std::vector<int m;
...
std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end());

This is the traditional way. You can also attemp to make ComparisonOp
into a template if you wish.

------------------------------------------------
#include <vector>
#include <algorithm>
#include <functional>

class ComparisonOp : public std::binary_fun ction<bool, int, int>
{
public:
result_type operator()( const first_argument_ type &a,
const second_argument _type &b ) const
{
return (a < b);
}
};

int
main()
{
std::vector<int m;
// fill m with elements
std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end(),
ComparisonOp()) ;
}
----------------------------------------------------------

This uses boost lambda.
----------------------------------------------------------
#include <vector>
#include <algorithm>
#include <boost/lambda/lambda.hpp>

// this works if operator< is defined for your type (int in your case)

using namespace boost::lambda;

int
main()
{
std::vector<int m;
// fill m with elements
std::vector<int >::iterator p =
std::max_elemen t( m.begin(), m.end(), (_1 < _2) );
}

-------------------------------------------------------------

[Piyo]

Re: get the max &quot;absolute& quot; integer in a vector

Piyo wrote:

JDT wrote:

>Hi,
>>
>Can someone provide me an example that uses std::max_elemen t()
>(probablly the predicate version) to return the max "absolute" integer
>in a vector? Your help is much appreciated.
>>
>Tony
>>
>ps.
>>
>// return the max integer in a vector
>std::vector<in tm;
>...
>std::vector<in t>::iterator p = std::max_elemen t(m.begin(), m.end());

>
This is the traditional way. You can also attemp to make ComparisonOp
into a template if you wish.
>
------------------------------------------------
#include <vector>
#include <algorithm>
#include <functional>
>
class ComparisonOp : public std::binary_fun ction<bool, int, int>
{
public:
result_type operator()( const first_argument_ type &a,
const second_argument _type &b ) const
{
return (a < b);
}
};
>
int
main()
{
std::vector<int m;
// fill m with elements
std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end(),
ComparisonOp()) ;
}
----------------------------------------------------------
>
This uses boost lambda.
----------------------------------------------------------
#include <vector>
#include <algorithm>
#include <boost/lambda/lambda.hpp>
>
// this works if operator< is defined for your type (int in your case)
>
using namespace boost::lambda;
>
int
main()
{
std::vector<int m;
// fill m with elements
std::vector<int >::iterator p =
std::max_elemen t( m.begin(), m.end(), (_1 < _2) );
}
>
-------------------------------------------------------------

Oops I fogot to put the abs function/fabs if float/double
in there but you get, the idea :)

HTH

[David Harmon]

Re: get the max &quot;absolute& quot; integer in a vector

On Wed, 14 Mar 2007 00:56:16 GMT in comp.lang.c++, JDT
<jdt_young@yaho o.comwrote,

>Hi,
>
>Can someone provide me an example that uses std::max_elemen t()
>(probablly the predicate version) to return the max "absolute" integer
>in a vector? Your help is much appreciated.
>
>Tony
>
>ps.
>
>// return the max integer in a vector
>std::vector<in tm;
>...
>std::vector<in t>::iterator p = std::max_elemen t(m.begin(), m.end());

I don't think I understand your question. Are you asking how to get
from the iterator p to the vector element value?

[JDT]

Re: get the max &quot;absolute& quot; integer in a vector

Hi Piyo,

I totally understand your solution and appreciate your help. I wonder
if there is a way to put different, existing STL algorithms together to
achieve the same function as your class ComparisonOp? Any further help
is appreciated.

Tony

Piyo wrote:

Piyo wrote:
>

>JDT wrote:
>>

>>Hi,
>>>
>>Can someone provide me an example that uses std::max_elemen t()
>>(probablly the predicate version) to return the max "absolute"
>>integer in a vector? Your help is much appreciated.
>>>
>>Tony
>>>
>>ps.
>>>
>>// return the max integer in a vector
>>std::vector<i ntm;
>>...
>>std::vector<i nt>::iterator p = std::max_elemen t(m.begin(), m.end());

>>
>>
>This is the traditional way. You can also attemp to make ComparisonOp
>into a template if you wish.
>>
>------------------------------------------------
>#include <vector>
>#include <algorithm>
>#include <functional>
>>
>class ComparisonOp : public std::binary_fun ction<bool, int, int>
>{
>public:
> result_type operator()( const first_argument_ type &a,
> const second_argument _type &b ) const
> {
> return (a < b);
> }
>};
>>
>int
>main()
>{
> std::vector<int m;
> // fill m with elements
> std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end(),
> ComparisonOp()) ;
>}
>----------------------------------------------------------
>>
>This uses boost lambda.
>----------------------------------------------------------
>#include <vector>
>#include <algorithm>
>#include <boost/lambda/lambda.hpp>
>>
>// this works if operator< is defined for your type (int in your case)
>>
>using namespace boost::lambda;
>>
>int
>main()
>{
> std::vector<int m;
> // fill m with elements
> std::vector<int >::iterator p =
> std::max_elemen t( m.begin(), m.end(), (_1 < _2) );
>}
>>
>-------------------------------------------------------------

>
Oops I fogot to put the abs function/fabs if float/double
in there but you get, the idea :)
>
HTH

[JDT]

Re: get the max &quot;absolute& quot; integer in a vector

David Harmon wrote:
Hi David,

That's not what I meant. What I need is a predicate that compares the
absolute values of the vector elements. It's best that the predicate is
composed of some existing STL algorithms, predicates and/or containers.
Thanks.

Tony

On Wed, 14 Mar 2007 00:56:16 GMT in comp.lang.c++, JDT
<jdt_young@yaho o.comwrote,
>

>>Hi,
>>
>>Can someone provide me an example that uses std::max_elemen t()
>>(probablly the predicate version) to return the max "absolute" integer
>>in a vector? Your help is much appreciated.
>>
>>Tony
>>
>>ps.
>>
>>// return the max integer in a vector
>>std::vector<i ntm;
>>...
>>std::vector<i nt>::iterator p = std::max_elemen t(m.begin(), m.end());

>
>
I don't think I understand your question. Are you asking how to get
from the iterator p to the vector element value?
>

[Piyo]

Re: get the max &quot;absolute& quot; integer in a vector

JDT wrote:

Hi Piyo,
>
I totally understand your solution and appreciate your help. I wonder
if there is a way to put different, existing STL algorithms together to
achieve the same function as your class ComparisonOp? Any further help
is appreciated.
>
Tony
>

OH, Ok. Then get the min and max of the vector and then negate
the min and max if any are negative and then get the max of those.
Is that what you are talking about? Each step can be done with
existing stl algorithms.

Or were you thinking of something else?

HTH

[Piyo]

Re: get the max &quot;absolute& quot; integer in a vector

JDT wrote:

Hi Piyo,
>
I totally understand your solution and appreciate your help. I wonder
if there is a way to put different, existing STL algorithms together to
achieve the same function as your class ComparisonOp? Any further help
is appreciated.
>
Tony
>
Piyo wrote:
>

>Piyo wrote:
>>

>>JDT wrote:
>>>
>>>Hi,
>>>>
>>>Can someone provide me an example that uses std::max_elemen t()
>>>(probablly the predicate version) to return the max "absolute"
>>>integer in a vector? Your help is much appreciated.
>>>>
>>>Tony
>>>>
>>>ps.
>>>>
>>>// return the max integer in a vector
>>>std::vector< intm;
>>>...
>>>std::vector< int>::iterator p = std::max_elemen t(m.begin(), m.end());
>>>
>>>
>>This is the traditional way. You can also attemp to make ComparisonOp
>>into a template if you wish.
>>>
>>------------------------------------------------
>>#include <vector>
>>#include <algorithm>
>>#include <functional>
>>>
>>class ComparisonOp : public std::binary_fun ction<bool, int, int>
>>{
>>public:
>> result_type operator()( const first_argument_ type &a,
>> const second_argument _type &b ) const
>> {
>> return (a < b);
>> }
>>};
>>>
>>int
>>main()
>>{
>> std::vector<int m;
>> // fill m with elements
>> std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end(),
>> ComparisonOp()) ;
>>}
>>----------------------------------------------------------
>>>
>>This uses boost lambda.
>>----------------------------------------------------------
>>#include <vector>
>>#include <algorithm>
>>#include <boost/lambda/lambda.hpp>
>>>
>>// this works if operator< is defined for your type (int in your case)
>>>
>>using namespace boost::lambda;
>>>
>>int
>>main()
>>{
>> std::vector<int m;
>> // fill m with elements
>> std::vector<int >::iterator p =
>> std::max_elemen t( m.begin(), m.end(), (_1 < _2) );
>>}
>>>
>>-------------------------------------------------------------

>>
>Oops I fogot to put the abs function/fabs if float/double
>in there but you get, the idea :)
>>
>HTH

or here is another idea:

from <algorithm>
std::max
from <functional>
std::less

then
std::max( -a, a ) gives the absolute value
then less( max(-a,a), max(-b,b ) ) defines the less than
operator of the absoulte value.

Is this what you wanted?

[JDT]

Re: get the max &quot;absolute& quot; integer in a vector

Hi Piyo,

It's exactly what I meant. I am going to try your less( max(-a,a),
max(-b,b ) ) solution. Hope it will work. Thanks so much.

Tony


Piyo wrote:

JDT wrote:
>

>Hi Piyo,
>>
>I totally understand your solution and appreciate your help. I wonder
>if there is a way to put different, existing STL algorithms together
>to achieve the same function as your class ComparisonOp? Any further
>help is appreciated.
>>
>Tony
>>
>Piyo wrote:
>>

>>Piyo wrote:
>>>
>>>JDT wrote:
>>>>
>>>>Hi,
>>>>>
>>>>Can someone provide me an example that uses std::max_elemen t()
>>>>(probabll y the predicate version) to return the max "absolute"
>>>>integer in a vector? Your help is much appreciated.
>>>>>
>>>>Tony
>>>>>
>>>>ps.
>>>>>
>>>>// return the max integer in a vector
>>>>std::vector <intm;
>>>>...
>>>>std::vector <int>::iterat or p = std::max_elemen t(m.begin(), m.end());
>>>>
>>>>
>>>>
>>>This is the traditional way. You can also attemp to make ComparisonOp
>>>into a template if you wish.
>>>>
>>>------------------------------------------------
>>>#include <vector>
>>>#include <algorithm>
>>>#include <functional>
>>>>
>>>class ComparisonOp : public std::binary_fun ction<bool, int, int>
>>>{
>>>public:
>>> result_type operator()( const first_argument_ type &a,
>>> const second_argument _type &b ) const
>>> {
>>> return (a < b);
>>> }
>>>};
>>>>
>>>int
>>>main()
>>>{
>>> std::vector<int m;
>>> // fill m with elements
>>> std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end(),
>>> ComparisonOp()) ;
>>>}
>>>----------------------------------------------------------
>>>>
>>>This uses boost lambda.
>>>----------------------------------------------------------
>>>#include <vector>
>>>#include <algorithm>
>>>#include <boost/lambda/lambda.hpp>
>>>>
>>>// this works if operator< is defined for your type (int in your case)
>>>>
>>>using namespace boost::lambda;
>>>>
>>>int
>>>main()
>>>{
>>> std::vector<int m;
>>> // fill m with elements
>>> std::vector<int >::iterator p =
>>> std::max_elemen t( m.begin(), m.end(), (_1 < _2) );
>>>}
>>>>
>>>-------------------------------------------------------------
>>>
>>>
>>Oops I fogot to put the abs function/fabs if float/double
>>in there but you get, the idea :)
>>>
>>HTH

>
>
or here is another idea:
>
from <algorithm>
std::max
from <functional>
std::less
>
then
std::max( -a, a ) gives the absolute value
then less( max(-a,a), max(-b,b ) ) defines the less than
operator of the absoulte value.
>
Is this what you wanted?

[JDT]

Re: get the max &quot;absolute& quot; integer in a vector

Hi Piyo,

I tried your idea but didn't make it work. I am not familiar with STL
syntax. Could you kindly give me some hint? Thanks for your further help.

Tony

Piyo wrote:

JDT wrote:
>

>Hi Piyo,
>>
>I totally understand your solution and appreciate your help. I wonder
>if there is a way to put different, existing STL algorithms together
>to achieve the same function as your class ComparisonOp? Any further
>help is appreciated.
>>
>Tony
>>
>Piyo wrote:
>>

>>Piyo wrote:
>>>
>>>JDT wrote:
>>>>
>>>>Hi,
>>>>>
>>>>Can someone provide me an example that uses std::max_elemen t()
>>>>(probabll y the predicate version) to return the max "absolute"
>>>>integer in a vector? Your help is much appreciated.
>>>>>
>>>>Tony
>>>>>
>>>>ps.
>>>>>
>>>>// return the max integer in a vector
>>>>std::vector <intm;
>>>>...
>>>>std::vector <int>::iterat or p = std::max_elemen t(m.begin(), m.end());
>>>>
>>>>
>>>>
>>>This is the traditional way. You can also attemp to make ComparisonOp
>>>into a template if you wish.
>>>>
>>>------------------------------------------------
>>>#include <vector>
>>>#include <algorithm>
>>>#include <functional>
>>>>
>>>class ComparisonOp : public std::binary_fun ction<bool, int, int>
>>>{
>>>public:
>>> result_type operator()( const first_argument_ type &a,
>>> const second_argument _type &b ) const
>>> {
>>> return (a < b);
>>> }
>>>};
>>>>
>>>int
>>>main()
>>>{
>>> std::vector<int m;
>>> // fill m with elements
>>> std::vector<int >::iterator p = std::max_elemen t(m.begin(), m.end(),
>>> ComparisonOp()) ;
>>>}
>>>----------------------------------------------------------
>>>>
>>>This uses boost lambda.
>>>----------------------------------------------------------
>>>#include <vector>
>>>#include <algorithm>
>>>#include <boost/lambda/lambda.hpp>
>>>>
>>>// this works if operator< is defined for your type (int in your case)
>>>>
>>>using namespace boost::lambda;
>>>>
>>>int
>>>main()
>>>{
>>> std::vector<int m;
>>> // fill m with elements
>>> std::vector<int >::iterator p =
>>> std::max_elemen t( m.begin(), m.end(), (_1 < _2) );
>>>}
>>>>
>>>-------------------------------------------------------------
>>>
>>>
>>Oops I fogot to put the abs function/fabs if float/double
>>in there but you get, the idea :)
>>>
>>HTH

>
>
or here is another idea:
>
from <algorithm>
std::max
from <functional>
std::less
>
then
std::max( -a, a ) gives the absolute value
then less( max(-a,a), max(-b,b ) ) defines the less than
operator of the absoulte value.
>
Is this what you wanted?

[Piyo]

Re: get the max &quot;absolute& quot; integer in a vector

JDT wrote:

Hi Piyo,
>
I tried your idea but didn't make it work. I am not familiar with STL
syntax. Could you kindly give me some hint? Thanks for your further help.
>
Tony
>

>>
>from <algorithm>
>std::max
>from <functional>
>std::less
>>
>then
>std::max( -a, a ) gives the absolute value
>then less( max(-a,a), max(-b,b ) ) defines the less than
>operator of the absoulte value.
>>
>Is this what you wanted?

I would just stick it in a function
#include <algorithm>
#include <functional>
bool foo( int a, int b )
{
return std::less( std::max(-a,a), std::max(-b,b) );
}

// then
int
main()
{
std::vector<int m;
std::sort( m.begin(), m.end(), &foo );
}